The present invention relates generally to the braking system of an electrically powered vehicle. More particularly, this invention concerns an electro-hydraulic compensator for use in the braking system of an electrically powered vehicle.
In an electrically-powered vehicle, the electric motor engine typically has a torque that is practically constant for engine operating speeds, i.e., angular velocities, of from 0 to n rpm. Ordinarily, n most often is on the order of 1500. For engine operating rates greater than n rpm, torque of the motor generally diminishes in proportion to the engine operating rate. Power from the engine behaves differently than torque: the power increases with engine operating rate from 0 to n rpm, but remains constant thereafter.
By using the motor in the braking state, it is possible to recharge the batteries and thus increase vehicle operating range. The resisting torque, however, is practically equal to the engine torque at a given operating rate. Accordingly, resisting torque declines with increasing engine operating rate. Furthermore, the motor braking torque is insufficient to stop a vehicle that requires strong or rapid deceleration. It is therefore necessary to add a conventional hydraulic braking device to an electrically driven car to enhance the available braking torque. However, the sum total of braking actions from the hydraulic braking device and the resisting torque is then variable which leads to problems, especially for the propulsion elements. For example, there is a risk of having wheels lock at slow speeds.